Substantial strides have been made in recent years to develop wheelchairs that can provide handicapped persons with greater mobility. Battery powered, motorized wheelchairs have greatly increased the speed and distance which a person can travel without assistance from others.
However, motorized wheelchairs tend to be bulkier than nonmotorized wheelchairs and are not built to provide optional manual self propulsion by the occupant. The rear drive wheels are usually smaller than the rear wheels of a nonmotorized wheelchair and are usually mounted farther rearward than the wheels of a nonmotorized wheelchair. In a typical model in which heavy batteries are located at the rear of the chair, the central axis of the rear wheels must be moved behind the wheelchair seat back to preclude tipping of the wheelchair.
Furthermore, the wheelchair occupant cannot readily disconnect the rear wheels from the drive motors. These drive motors have considerable inertia and make manual propulsion of the wheelchair difficult while they are connected. The small size and rearward positioning of the rear wheels further adds to the difficulty of self propulsion. Typically a manual drive ring is not even provided on the rear wheels of a motorized wheelchair. It would be desirable to have a motorized wheelchair which the occupant could selectively disconnect from the motor drive system and manually self propel in situations where precise maneuvering is required, or some exercise for the user is desirable.